Local Area Networks (LANs) are widely used in the private and public sector to provide interconnectivity between computers affiliated with a building or site. LAN's typically consist of several computers connected together by a hardwired network. The hardwired network is often referred to as a system backbone. A server or host computer will also be connected to the backbone and serve as a central controller for the particular LAN. Recent advances in technology have also enabled LAN's to be used to interconnect wireless devices such as portable workslate computers, portable bar code readers, and the like. In such cases, access points or base stations are connected to the LAN to provide for wireless interfacing of such portable devices to the backbone.
Although connecting several computers or portable devices within a single building can readily be accomplished via the use of a LAN infrastructure, difficulties often arise when there exists more than one building or site which needs to be connected. Such is often the case on college campuses and businesses operating out of more than one building. For instance, in such cases it may be desirable to have a single host computer or server provide all buildings or sites with interconnected services such as e-mail and group directories. In order to utilize a single server and provide for communication between each building or site, some manner of interconnecting each LAN is needed.
One known method of interconnecting each LAN associated with a specified area is to physically make an additional hard wired connection between each LAN. Unfortunately, this is not only expensive and time consuming given the need to provide trenches and other passages for conduit and wiring to be installed between the sites, but also is oftentimes not possible when buildings are several miles apart or separated by parks, streams or other obstacles.
Consequently, wireless bridges have been developed in order to provide a method of connecting two or more LANs. A wireless bridge is a device which is physically connected to the LAN and can wirelessly transmit and receive data and other communications from other bridges connected to different LAN's. Thus, a wireless bridge allows several LAN's to become interconnected without the need for physically laying additional conduit and wiring.
As the number of installed LAN's increases, the need for bridging multiple LAN's together also increases. Thus, in order to bridge two or more remote LANs to the LAN having the main server, multiple bridges are connected to the LAN having the main server. Each of the bridges on the LAN having the main server is then dedicated to communication to a specified one of the remote LAN bridges. However, each bridge utilizes the same radio device and therefore communicate on the same frequency and same channel (i.e., in FH system the same hopping sequence, and in DS systems the same PN codes). In order to avoid in air collisions of data being transferred simultaneously between two different sets of bridges, each bridges time shares the airways using known time sharing protocols such as collision sense multiple access (CSMA). In a CSMA system, each bridge will effectively listen to the airway to ensure that it is free before transmitting information. More particularly, in a system operating under a CSMA protocol, each bridge "listens" to the signal traffic in the air before transmitting information in order to avoid collisions of packets containing information. If the air is busy with signal traffic, the bridge performs a random back off in order to allow time for the air to clear.
Unfortunately, as the number of installed LAN's which need interconnectivity increases, so does the wireless traffic which must be passed along. This often results in large system delays given that no two bridges can communicate at the same time. Furthermore, the cost associated with adding a bridge each time a new LAN is introduced can get expensive. Accordingly, there is a strong need in the art for a method and apparatus for cost effectively increasing the throughput associated with the bridging of multiple LANs together.